This invention relates to rubber modified polymeric compositions. Specifically, it relates to polymers modified with grafted rubbery polymers, said grafted rubbery polymers being formed from a process involving a hydroperoxidized rubbery polymer intermediate.
Rubber modified styrenic polymer compositions are well-known in the prior art. Exemplary of such compositions are compositions comprising polystyrene and a reinforcing, modifying rubbery polymer as well as compositions comprising styrene, acrylonitrile, and a reinforcing modifying rubbery polymer.
These rubber modified styrenic polymer compositions can be prepared in a variety of ways. Typically, one of two methods is used to produce such compositions. One method involves first producing a styrenic polymer (homopolymer or interpolymer), heat-plastifying said styrenic polymer, and blending said heat-plastifyed styrenic polymer with a heat-plastifyed grafted reinforcing rubbery polymer. Alternatively, the styrenic polymer can be polymerized in the presence of a preformed, ungrafted, rubbery polymer. For example, by a mass or bulk polymerization process, to obtain a rubber-modified styrenic polymer composition.
Prior art processes of preparing rubber modified styrenic polymer compositions have produced compositions having desirable physical properties. However, it is always desirable to improve the physical properties of such compositions. The compositions of the present invention possess physical properties superior to those compositions described by the prior art. Specifically, compositions according to the present invention possess an improved balance between izod impact strength and tensile strength.
Applicants have discovered that the present invention allows for the precise control of the average number of hydroperoxide groups per rubbery polymer chain, which in turn dictates the degree of grafting to the rubbery polymer. This precise control over the average number of hydroperoxide groups formed allows the compositions of the present invention to possess a specific izod impact/tensile strength balance thus allowing for production of compositions tailored for specific property needs.